The present invention relates to solid state lighting. Similar to fluorescent lighting, solid state lighting uses phosphors to realize the desired color output.
Commercial solid state lighting typically uses gallium nitride (GaN) semiconductor based blue light emitting diodes (LEDs), operating at a wavelength of 450-500 nanometers (nm), that excites a yellow-emitting phosphor, which is embedded in the epoxy dome, converting some of the blue LED light to a wavelength of about 560 nm. The combination of blue and yellow renders a white emitting LED.
The yellow emitting phosphor used in commercial solid state lighting is cerium doped yttrium aluminum garnet (YAG:Ce) crystals that have been ground up into a powder and bound in an epoxy host. The resulting YAG:Ce doped epoxy is then cast onto the GaN LED die. The yellow light stimulates the red and green receptors of the eyes and the resulting mix of blue and yellow gives the appearance of white light. This white light, however, has a blue color tint to it. This is referred to as cold light. Increasing the wavelength of the light emitted by the phosphor, so it emits red, can reduce or eliminates the blue tint. This produces what is referred to as warm light.
YAG:Ce is also very efficient in blue to yellow light conversion. Newer phosphor blends have been produced that add more energy in the red region of the spectrum to produce this warmer light; however, they reduce the efficiency of the light output. This can also increase the heat produced by the device.
Also, the heat produced by the GaN LED die itself degrades the epoxy/phosphor material, thus reduces the lifetime of the device.
The present invention uses a DNA-based biopolymer material as a host for phosphor guest materials that are used for solid state lighting, such as the yellow emitting phosphor used in commercial solid state lighting, cerium doped yttrium aluminum garnet (YAG:Ce) crystals that have been ground up into a powder.
The DNA-based biopolymer material of the present invention acts to enhance the light output and efficiency of solid state lighting and to red shift the light emission or shift the emission to longer wavelength. This renders brighter solid state lighting that operates at lower input power, with less heat generated and has longer lifetimes. It also reduces or eliminates the cold or blue tinted color of solid state lighting by warming or red shifting the emission in these devices.